1. Field of the Invention
This invention relates to polymerized beads, and more particularly to a process and apparatus for producing polymerized beads containing actives, such as perfumes and pesticides, from a solution of monomers and the actives.
2. Description of the Prior Art
The standard method in the art of producing polymerized beads containing actives is suspension polymerization. The suspension polymerization process typically begins with a vat of monomer solution containing the actives in a suspending medium, usually water. The liquid is stirred to disperse the monomer and actives solution as droplets throughout the suspending medium. Polymerization is initiated by a chemical initiator or other initiation means suitable for the particular monomer or monomers being polymerized. The solution is stirred as the monomers polymerize into beads.
A uniform bead size is usually desirable. A uniform size is especially desirable to achieve a uniform release rate for actives contained within the beads. Uniformity in bead size is difficult to achieve with suspension polymerization. It would therefore be desirable to provide a process and apparatus for polymerizing beads whereby the size of the polymerized beads could be controlled.
Suspension polymerization is inefficient, as it is necessary to heat both the monomer and actives solution, and the suspending medium, to the reaction temperature. The suspending medium can have more than three times the weight of the monomer and actives solution, and the heating process can therefore require a large amount of energy.
Suspension polymerization is also relatively expensive due to the large amount of water that is necessary both to conduct the reaction, and to wash the resulting bead product. This water must be treated as a waste, and the disposal is expensive.
The use of irradiation to effect polymerization is known. Stewart, Jr., et al, U.S. Pat. No. 3,215,612 disclose a process and apparatus for preparing polymeric particles by irradiating a momomer mixture, particularly unsaturated aldehydes, with high energy electrons, protons and photons while maintaining the mixture in an agitated state with an inert gas. Shutze, et al, U.S. Pat. No. 2,914,452 disclose a process for polymerizing unsaturated hydrocarbons by irradiation. The use of ultraviolet light in polymerization reactions is disclosed by U.S. Pat. No. 3,549,366.
It would be desirable to provide a process and apparatus for polymerizing beads containing actives such as perfumes and pesticides that are economical, efficient, and that do not require the disposal of substantial amounts of waste materials. It further would be desirable to provide such a process and apparatus wherein the bead size could be controlled. It also would be desirable to provide a process and apparatus which would not require substantial washing of the bead product.